Place the diced potatoes in a pot and cover with water. Bring to a boil over medium-high heat and cook until potatoes are tender, about 10-12 minutes.
Drain the potatoes and transfer them to a bowl. Mash the potatoes until smooth. Set aside.
Heat the vegetable oil in a small pan over medium heat. Add cumin seeds and mustard seeds and cook until they start to pop, about 1 minute.
Add the chopped onion to the pan and sauté until translucent, about 3-4 minutes.
Add garam masala, turmeric powder, red chili powder, and salt to the pan. Stir well and cook for 1 minute.
Add the mashed potatoes to the pan and mix thoroughly with the spices and onions. Cook for 2-3 minutes, stirring occasionally.
Remove the pan from heat and stir in the chopped cilantro. Let the filling cool to room temperature.
In a small bowl, mix all-purpose flour and water to create a smooth paste. This will be used as glue for sealing the spring rolls.
Lay one spring roll wrapper on a clean surface with one corner pointing towards you (diamond shape). Place about 2 tablespoons of the mashed potato filling near the corner closest to you.
Fold the corner over the filling, then fold the left and right corners inward, and roll tightly towards the top corner. Seal the edge with the flour paste.
Repeat the process with the remaining wrappers and filling.
Preheat the air fryer to 375°F (190°C) for 3 minutes.
Lightly brush or spray the spring rolls with vegetable oil on all sides.
Place the spring rolls in the air fryer basket in a single layer, making sure they do not touch.
Air fry at 375°F (190°C) for 12-15 minutes, turning halfway through, until the spring rolls are golden brown and crispy.
Remove from the air fryer and let cool for 2 minutes before serving.